Burner apparatus



G. H. GARRAWAY BURNER APPARATUS INVENTOR G'EQRGE A H. GARRAWAY ATTORNEYSDec. 3, 1957 Filed June 29. 1951 Dec.-3, 1957 G, H. GARRAWAY 2,815,069

BURNER APPARATUS Filed June 29. 1951 5 Sheets-Sheet 2 T MM Miu' 'y IULT# 26 INVENTOR GEORGE H. GARR/AWAY l' A |`IIII .BY/JWM@ l ATTORNEYSDec. 3, 1957 G. H. GARRAWAY 2,815,069

BURNER APPARATUS Filed June 29, 1951 5 Sheets-Sheet 3 INVNTOR GEORGE H.GARR/AWAY ATTORNEYS Dec. 3, 1957 G. H. GARR/AWAY 2,815,069

BURNER APPARATUS' Filed June 29. 1951 5 Sheets-Sheet 4 ,//9 [da IINVENTOR GEORGE H. GARRAWAY ATTORNEYS Dec. 3, 1957 G. H. GARRAWAY2,315,069

BURNER APPARATUS Filed June 29. 1951 l 5 sheets-sheet 5 /20 5 .71.75 R T/30 /26 /WT /z/ dTT.

INVENTOR GEORGE H. GARRAWAY ATTORNEYS United States Patent C BURNERAPPARATUS George H. Garn-away, Wyomssing, Pa., assignor to Orr &Sembower, Inc., Reading, Pa., a corporation of Penn- SylvaniaApplication June 29, 1951, Serial No. 234,198

Claims. (Cl. 158--76) This invention relates to improvements in fuelburner constructions and more particularly to improvements in fuelburners for use with relatively small capacity steam generating units ofthe type usually used for producing process steam and adapted to burneither liquid or gaseous fuel.

It is one of the primary objects of my invention to provide a fuelburner apparatus of an improved construction resulting in more ehicientcombustion of liquid fuels and the elimination of formation of carbondeposits in the fuel injector assembly and upon the internal walls ofthe steam generating unit.

In prior art liquid fuel injectors, much ditiiculty has also beenencountered due to the formation of carbon deposits in the outletorifice and fuel channels of the fuel nozzle. These carbon depositsresult primarily from the coking of the liquid fuel remaining in thenozzle after the fuel supply has been shut off under the effect of theintense heat to which the end portion of the nozzle is subjected fromthe slowly cooling refractory lining of the furnace. During burneroperation, the atomizing uid and liquid fuel passing through the nozzleeffectively dissipate the heat to which the end of the nozzle issubjected, but, upon termination of operation, the full intensity of theheat from the refractory furnace lining adjacent the nozzle outlet iseffective to heat the nozzle. In such prior art fuel injectors, frequentcleaning of the fuel passages of the nozzle is necessary to eliminatethis carbon accumulation.

It is, accordingly, a further important object of this invention toprovide a liquid fuel injector of an improved construction by whichaccumulation of carbon deposits inthe nozzle passages is eliminated. j

More specifically, it is an important object of this invention toprovide a liquid fuel injector of an improved construction wherein heattransfer channels and heat transfer blocks are utilized to preventheating of the walls of the fuel channels within the nozzle sufiicientlyto produce carbon ydeposits and to effect transfer of the heat to whichthe nozzle is subjected to members of the burner assembly where the heatcan be dissipated without producing coking of the fuel.

A further object of this invention is the provision of liquid fuelinjector assembly of an improved construction wherein the heat to whichthe nozzle is subjected during burner operation is utilized foradditional preheating of the atomizing fluid such as air or steam toproduce more eliicient overall burner operation.

In prior art fuel injectors, certain difficulty has also resulted fromthe tendency, after the burner has been shut off, of the liquid fuelremaining in the fuel conduit leading to the nozzle to run out slowlyonto the refractory lining of the combustion chamber or into theatomizing fluid supply passages of the nozzle. The accumulation of fuel,resulting from this leakage, produces poor burner starting conditionsand inelhcient overall operation resulting in the initial injection ofunatomized liquid fuel and the burning of fuel directly on the furnacewalls.

A still further important object of this invention is, therefore, toprovide a liquid fuel injector of an im proved construction whereinleakage of fuel from the fuel supply pipe through the fuel passages: ofthe nozzle is prevented after termination of burner operation.

More specifically it is an object of this invention to provide a fuelinjector of an improved construction including a fuel stop whichprevents leakage of fuel from the fuel supply conduit when the fuelsupply is cut olf but which does not inhibit fuel flow during burneroperation.

These and other important objects of this invention will become apparentas the description thereof proceeds in reference to the accompanying`drawings wherein corresponding reference numerals designate like partsthroughout the several views and wherein:

Figure 1 is partially sectional view of a burner assembly according tothe invention adapted to burn alternatively either liquid or gaseousfuel;

Figure 2 is a sectional view of that assembly taken along the line 2-2of Figure l;

Figure 3 is a sectional view chiefly illustrating the air guidestructure within the air plenum taken along the line 3-3 of Figure l;

Figure 4 is an exploded perspective view showing the several parts ofthe burner assembly adapted for use with gaseous fuel;

Figure 5 is a sectional view of the burner assembly as adapted for useonly with gaseous fuel;

Figure 6 is a vertical sectional view of a fuel burner apparatus adaptedto burn liquid fuel only;

Figure 7 is an enlarged vertical sectional view of the liquid fuelinjector of the burner apparatus of Figures 1 and 6;

Figure 8 is an enlarged exploded view in section o'f the core, cap, andbody members of the nozzle assembly of the fuel injector of Figure 7;

Figure 9 is a front end view of the nozzle assembly core member;

Figure l0 is a rear end view of the nozzle assembly core member;

Figure l1 is a front end view of the nozzle assembly Cap;

Figure 12 is a rear end view of the nozzle assembly body member;

Figure 13 is a fragmentary sectional view of the nozzle assembly takenalong the lines 13-13 of Figure l1; and

Figure 14 is a perspective view of the liquid fuel stop of the fuelinjector of Figure 7.

A burner of an improved construction which is adapted to burneffectively either liquid or gaseous fuels is disclosed in Figure l. Inthis burner, means are provided for surrounding a centrally injectedstream of fuel with a mass of axially flowing primary air sufficient forinitial combustion and with a spiraling mass of secondary air suicientto complete combustion. When liquid fuel such as oil is used, the fuelis atomized and sprayed into the primary air stream in the combustionchamber to assure proper iutermixing, whereas, when gaseous fuel isused, the primary air and gaseous fuel are intermixed in a premixingchamber prior to introduction into the combustion chamber. The air flowguide structure is such that the relative proportion of primary tosecondary air may be set by the proper selection of the size of ringscontrolling the size of the primary and secondary air orices for maximumrating of the boiler and such that the total quantity of air suppliedmay be reduced for operation at a fraction of such maximum ratingwithout disturbing either the established air pattern or the relativeproportion of primary to secondary air.

Air guide structure In this burner structure, a housing providing a mainair chamber or plenum is xed `to the end of the tire or combustionchamber 12 of a boiler as by bolts 14. Air plenum 10 is generallycylindrical in cross section,

Y as shown in Figure 2, having a downwardly open air inlet port 16 4andan axially open outlet port 13 through its end adjacent the combustionchamber as shown in Figure 1. Outlet port 18 is coaxially aligned with afrustoconical wall 20 of the refractory lining of the combustion chamberand with the generally cylindrical contour of air .plenum 11i. As isbest shown in Figure 2, the internal surface of wall 22. of the inletport 16 is tangential to the inner cylindrical surface 23 of the airplenum 10. the space between wall 22 and the edge 24 of the interruptedcylindrical wall of the air plenum defining the maximum possible openingof the inlet port.

inlet port 16 is connected by a suitable flexible air duct 26 to theoutlet 28 of a blower (not shown) in a conventional manner. In thisstructure,`the stream of incoming air is introduced under pressure atsubstantially constant `velocity into the air plenum 10 through inletpassage 16, forming a moving ylayer or film of air adjacent wall 2.2 ofa radial thickness equal to the distance between wall 22 and edge`24.This air stream entering the plenum 18 tangential to the cylindricalwall 23 will Afollow a generally circular path around the cylindricalwall 23 as indicated by the arrow 29 in Figure 2.

Means are provided for controlling the volume of incoming air by varyingthe thickness of the air stream entering the inlet along wall 22 withoutdisturbing the tangential flow of the incoming air stream. A throttlevalve, which may be adjusted to vary the size of the opening at 24, isdisclosed as a plate member 30 having an arcuate outer surface 32 and aninner surface 34 suitably curved or streamlined as shown to produceminimum turbulence of the passing air stream. Plate member ,Sil issuitably xed to pivot arms 36 and 38 which are in turn fixed to pivotshaft 4t! journalled in the walls 42 and 44 of the inlet passage 16 asshown in Figure l. Any suitable control linkage for positivelypositioning shaft 411 may be provided. Such linkage is actuated by athrottle valve control means (not shown) which will also control thequantity of fuel introduced into the burner in a conventional manner. Bythis valve struc ture, the quantity of air introduced into the airplenum may be varied in accordance with the load upon the burner withoutsubstantially modifying the input velocity of air into the air plenum atthe throttle valve. The air input velocity is controlled atapproximately 65 feet per second (a tolerance of +10% to 15% beingpermissible). Since the control means for plate member 30 forms, per se,no part of this invention, it has neither been shown or described.

Since, as is shown in Figure 2, shaft is parallel to wall 22, platemember 31) may be swung toward wall 22 to reduce the opening of theinlet port 16. Suitable stops are provided to limit the `travel of platemember 36, a shoulder 46 being formed integrally with the inlet portwall establishing the maximum open position of this iniet throttle valvewhile an adjustable stop 48 limits the closing of the inlet valve.Because plate member 30 moves toward wall 22, the thickness of the airstream and thereby the quantity of incoming air may be reduced withoutdisturbing the tangential inflow of the air stream while the input airvelocity is maintained approximately constant. Since the air pressurewithin the air plenum 11B is greater than that within the re chamber 12due both -to the draft ofthe furnace and to the air input blower, theair stream owing into the air plenum and travelling circumferentiallytherearound, substantially spirals toward the outlet port 18.

' 4 Gaseous fuel injection and mixture As shown in Figure 1, a gasplenum housing 50 having a radial inlet port 52 issecured as by bolts 54to the outer end of the air plenum 10 opposite its outlet port 18. Thatend of the air plenum 10 is formed with a large opening S6 for which the.ange portion 58 of the gas plenum 50 serves as a cover. The wall 60 ofthe gas plenum 50 is formed with an opening 62 therethrough in axialalignment with the outlet port 18. A tubular member 64, having a ange 66axed thereto at one end, is secured to the wall 60 of gas plenum at theopening 62 as by bolts 68. Tubular member 64 extends from the wall 60coaxially through the air plenum 10 to the outlet port 18. A primary airbaflie 70, which is fixed within the tubular member 64 as by set screws71, is formed internally with an annular surface of revolution 72converging toward the outlet port 18. The rear portion 74 of tubularmember 64 and the throat of primary air baffle 70 togetherform a gasnozzle assembly for directing the ow of gaseous fuel from the gas plenumE@ toward the combustion chamber 12 through the center of the outletport 18. This is clear in Figure 5. The cross sectional area of thenozzle formed by surface 72 is so proportioned relative to the gaseousfuel supply pressure that the exit velocity of the gaseous fuel'isbetween 29 and 60 feet per second at maximum load.

Air guide structure isprovided within the air plenum 10 for segregatingthe air circulating therein into primary and secondary air streamssurrounding the centrally in jected fuel to supply the air necessary forcombination. The primary air stream for initial combustion enters thecombustion chamber 12 through the forward portion of the tubular member64, ahead of bafde 70, while the secondary air stream constituting t-heremaining air necessary for complete combustion enters through port 18around the ouside of tubular member 64. The crosssectional area of theprimary orifice i-s determined by the internal diameter of a toroidalbody 76, known as a lprimary air ring, mounted within the inner end ofnozzle member 64 as by screws 78. The cross-sectional area of thesecondary air orifice is fixed by a toroidal body 77, known as thesecondary air ring, secured around the inner end of the tubular member64 adjacent outlet port18, as by set screws 79.

These air rings 76 and 77, being secured on tubular member 64 only byset screws 78 and 79, are readily removable from the air guidestructure. The relative proportion of primary to secondary air iscontrolled entirely by the relative sizes of the primaryfand .secondaryair rings 76 and 77 which provide accurate annullanrnetering orifices.Air rings 76 and 77 areof such relative'size;

that the primary air stream constitutes from 40 to SI5-.per-V cent ofthe total combustion air and the primary and secondary air orifices are.of -such size that the average of the primary and secondary airdischarge velocities is be-L tween 140 and 200 feet per second atmaximum burner rating. aj, I;

The primary air enters tubular member 64 throughfjaseries of holes 80through the walls thereof forwardly/Lof the area at which the gas nozzle7i) is xed.- Air isidirected 4radially through these holes 80 by astationary air compressor assembly 81 having an annular-frow oflongitudinally extending guide vanes or air scoops 82, which aresupported in xed position between a pair of annular supports 84 and 86.Thisy stationaryair compressor assembly 81 is mounted coaxially on thetubular member 64 by a ring 88 which is secured thereto by any suitablemeans such as set screws 89 and which is secured to the support 84 as bybolts 90.` A cone 92 is mounted between support 86 and secondary airring 77. Cone 92 provides a ow directing surfa'c'e for the secondaryair,

. and structurally it reenforcesthe assembly.

erally cylindrical air plenuirii from the inlet port 16 toward theoutlet port 18. As viewed vin Figure 3, this circulation is in acounterclockwise direction. A` portion of this circulating air willstrike the stationary air scoops 82 and be directed radially inwardthrough the holes 80 of tubular member 64.

The dissipation of the velocity of the air so directed will result ingreater air pressure within the compressor assembly 81 and withintubular member 64. The aggregate cross-sectional area of the holes 80must be considerably greater than that ofthe opening through the primaryair ring 76, being in the order of from fifty to seventy-five percentgreater, a range of from sixty-five to seventy-tive percent beingpreferable. There being no substantial pressure differential between theexterior and interior surfaces of the shell of tubular member 64, therelative proportion of the` primary and secondary air is controlled bythe sizes of the primary and secondary air rings 76 and 77. The externalsurface 94 of the gas nozzle 70 is a smooth surface of revolutionconverging toward the outlet port 18, the nozzle 70 being of such lengththat surface 94 extends slightly beyond the forwardrnost of the holes 80and of such size that the velocity of the primary air toward the primaryair orifice is approximately one hundred five feet per second at maximumburner load, the effective annular primary air metering area definedbetween the orice end of surface 94 and the internal wall of member 64being in the range of 33 to 50 percent greater than the cross-sectionalarea of the primary air outlet orifice. Surface 94 thus serves as aprimary air baille to redirect the radially entering primary air in anannular, expanding air stream owing axially toward the iire chamber 12through primary air ring 76.

The component parts described thus far constitute the structure of thegaseous fuel burner. A view showing these elements assembled for usewith gaseous fuel only is shown in Figure 5, this structure differingfrom that of Figure l solely in the omission of the liquid fuel injectorassembly 96 and its replacement by a cover plate 97. When gas is burned,the gaseous fuel passes from the lgas plenum 50 through the tubularmember 64 and the nozzle 70 toward the orice formed by primary air ring76. The annular primary air stream enters the forward end of tubularmember 64 and flows axially over surface 94 toward the primary air ringorifice.

The portion of tubular member 64 forwardly of the smaller end of nozzle70 serves as a premixing chamber for the primary air and the gaseousfuel to insure the necessary intermixing of fuel and air before thestream reaches the combustion zone within the re chamber 12. Thispremixing of air and fuel occurs within tubular member 64 and at theprimary air ring 76. The internal cross-sectional area of the portion ofmember 64 forming the primary air or premixing chamber in front ofnozzle 70 is preferably from 50 to 75 percent greater than thecross-sectional area of the primary air outlet orice defined by ring 76in order to maintain proper air and fuel velocities for optimumpremixing. In order to assure proper mixing and proper gaseous fuelvelocities, the cross-sectional area of the discharge end of nozzle 70is from 65 to 77 percent of said primary air outlet orificecross-sectional area.

A suitable igniter (not shown) is provided near the mouth of outletportlS. As the charge of intermixed gaseous fuel and primary air isintroduced into the fire chamber it is further surrounded with aspiralling mass of secondary air which intermixes with the expandingburning fuel to insure complete combustion thereof.

Liquid fuel injection As mentioned at the outset, the burner assembly ofFigure 1 is adapted to burn either liquid or gaseous fuel. When liquidfuel is to be used in the combination burner of Figure l, the gas supplyis merely cut off below port 52. In order to introduce'liquid fuel intothe fire chamber in a formvsuitablefor combustion, the .liquid fuelinjector 96, now to be described, which is provided for injecting theliquid fuel in the form of an atomized spray into the center of theprimary air stream, may be coupled for use with the previously describedair guide structure without the gaseous fuel injector. Such anarrangement is shown in Figure 6.

When the burner assembly l is so modified, a cover member 50 is securedas by bolts 54 to the outer end of the air plenum 10 opposite its outletport 18 over the large access opening 56 in lieu of the gas plenum 50.The interior wall 60 of the cover member 50 is formed with recess 62therein in axial alignment with the outlet port 18, and the tubularmember 64, having the flange 66 affixed thereto, is secured to the wall60 of cover member Sti at the recess 62 by the bolts 68. Tubular member64 extends from the wall 60 coaxially through the air plenum 10 to theoutlet port 18. The primary air battle 76 is txed within the tubularmember 64 by the set screws 71 and is formed internally with the annularsurface of revolution 72 converging toward the outlet port 18, aspreviously described in reference to Figures l and 5. The air guidestructure, which is identical with that shown in Figures l and 5,functions in the manner previously set forth.

As mentioned at the outset, in order to attain eilicient fuel combustionand eliminate the formation of carbon on the refractory and heattransfer walls of the combustion chamber, liquid fuel is preferablyinjected into the combustion zone in the form of a short bushy flame. Anexample of the dimensions of such a ame as compared with the dimensionsof a combustion chamber will perhaps best illustrate what is meant by ashort bushy flame.

In an eighty horsepower boiler of the type illustrated, which is one ofmany to which the present invention is applicable, the combustionchamber formed by the heat transfer surfaces is in the form of acylinder approximately ninety inches long and approximately twentyinches in diameter. For such a combustion chamber, a coaxiallyintroduced short bushy flame at maximum burner load, for example,twentyfour gallons of fuel per hour, would preferably have an overalllength of from fifty-tive to sixty inches from the nozzle dischargeorifice, the flame starting within an inch or less from the nozzle. Atthe nozzle end of theflame it would preferably have a diameter ofapproximately eight inches and gradually increase in diameter `toapproximately eighteen inches at a distance of about forty inches fromthe nozzle. As the: load upon the burner is reduced below maximum, theflame dimensions are reduced proportionately.

A ame of this general configuration produces optimum combustionconditions in a minimum space. The liquid fuel injector of the presentinvention, hereinafter to be described in detail, in cooperation withthe air guide structure previously described produces a llame having theforegoing short bushy configuration and may be used with combustionchambers having other than a cylindrical cross-sectional configurationto attain similarly advantageous combustion conditions,

It is to be understood that the foregoing flame dimensions are merelyillustrative of what is meant by a flame which is short and bushyrelative to the length and crosssectional dimensions of a combustionchamber and that such dimensions will vary in accordance with the loadand load capacity of the burner.

The liquid fuel injector assembly 96, which is constructed according tothe present invention and which is adapted to produce a short bushyflame such as that described above, includes a pair of concentric tubes98 and 100, on the lire chamber end of which is mounted an atomizingnozzle assembly 102 and on the other of which is mounted an oil andatomizing fluid inlet fixture 104. This fixture may be of the form shownbut is preferably v of the form disclosed in application Serial No.213,068

7 filed on February 28, 1951 by Garraway and Kirkup for Fuel FlowControl, now Patent No. 2,753,927. Fuel injector assembly 96 is rigidlysupported in its coaxial position within tube 64 by fixture 104 which issecured by bolts 106 to the rear end of the cover plate 50. Fixture 104is formed with inlet ports 110 and 112 which are connected by suitableconduits 114 and 116 to a source of liquid fuel such as fuel oil and toa source of pressurized atomizing fluid, such as air or steamrespectively. Fixture 104 is provided with an end bore 111 into whichatomizing fluid inlet port 112 opens, and at the bottom of bore 111 areduced threaded bore 113 opens into oil inlet port 110. Tube 100 hasits outer end threaded to interfit with bore 113 so that all oilentering the assembly is delivered into tube 100. The surrounding tube98 extends tightly into bore 111 to communicate directly with atomizingfluid inlet port 112. Tube 98 is mounted on fixture 104 by a pilotingflange 118 which is suitably secured to the exterior of tube 98 andmounted on fixture 104 as by screws 119. If desired, flange 118 may beintegral with tube 98. Suitable cutoff and control valves (not shown)are provided in the inlet conduits 114 land 116 in a conventional mannerto control the flow of fuel and pressurized atomizing fluid. The fuelcontrol valves are actuated with the air throttle valve in accordancewith the load on the boiler while that for the atomizing fluid remainsin its initially adjusted position regardless of the load.

Neozzle assembly Compressed air from conduit 98 atomizes the oil fromconduit 100 at the nozzle assembly 102 to spray the oil in fineparticles into the fire chamber 12. The structure of the nozzle assembly102 is of the improved type which is shown in Figures 7 to 13. As shownin Figure 7, the nozzle assembly 102 consists primarily of threemembers: a cylindrical core member 120, an annular disc shaped capmember 121, and a hollow cylindrical body member 122. In their assembledposition, core 120 fits snugly with the cylindrical inner wall 122 ofbody 122, and cap 121 is clamped within the body member between the core120 and the end wall of body member 122, the relative axial position ofthese members being maintained by the abutment of the rear end of coremember 120 against the end of atomizing fluid tube 98 when the bodymember 122 is tightly secured upon tube 98 by the threaded connection123 therebetween.

The core member 120, as is best shown in Figures 8 and l0, is formedwith a central end bore 124 into which the forward end of the fuel tube100 snugly projects. A flexible O-ring 126 preferably formed of rubberis provided in an annular groove 126' on tube 100 to prevent leakagebetween the oil passage and the atomizing fluid passage through tube 98.Core 120 is provided with a reduced head 127 connected to itscylindrical main portion by a further reduced neck 128 formed by anannular groove 129. A plurality of small parallel bores 130concentrically arranged about the longitudinal axis of the core provideatomizing fluid passages from tube 98 into groove 129 and annularchamber 131 within the body surrounding head 127.

The end of head 127 and the adjacent side of cap 121 are formed withmating conical surfaces 132 and 133 respectively which are tightly heldin contact in the assembly. A plurality of atomizing fluid conductingslots 134 are cut in surface 132 of the head, and a plurality ofinclined oil conducting passages 135, one for each slot, are formedthrough the neck and head of the core 'for connecting bore 124 with theslots 134 intermediate the ends of latter. All of slots 134 are arrangedat the same .radial angle with respect to the axis of the core, eachtbeing perpendicular to a radius of the core and since they are formedin conical surface 132 they are all inclined axially at the same anglewith lrespe'ct to the `core axis. At its tip., head -127 is cut back toprovide a conical -face 136 adjacent the ends of slots 134.

As illustrated lin Figure 8, slots 134 have gradually decreasingcross-sectional area until they intersect the oil passages and are thenof constant cross-section for the remainder of their lengths.

On the end opposite converging surface 133, cap 121 is formed with adiverging smooth annular surface 137, and an annular orifice 138 havinga narrow flat lip is formed therebetween. Surface 137 is a surface ofrevolution described by a curved line moving about the longitudinal axisof the cap. The end wall of body 122 is formed with a similar convergingsmooth surface of revolution 139, the edge 139 of which, in theassembly, is a smooth continuation of edge 140 0f surface 137. The edge141 of surface 139 denes the exit orifice of the nozzle assembly 102.

As illustrated in vFigure 7, surfaces 137 and 139 define in the assemblya to'roidal mixing dome 142 symmetrical about the nozzle axis and intowhich a plurality of streams of mixed oil and atomizing fluid aretangentially directed to produce an expanding swirling atomized fuelmixture within dome 142 that spirals out through the orifice 141.

As pointed out at the outset, in order to avoid fuel impingement on theheat transfer surfaces or the refrac'tory material 0f the furnace liningand to produce complete combustion of the fuel in a short chamber, it isnecessary to inject the liquid fuel into the furnace combustion zone inthe form of a fine mist and in such a manner as to produce a short bushyflame. I have discovered that this desired result may be produced byproperly controlling the relation of the pressure of the atomizingfluid, the relative proportion of the atomizing fluid to the injectedfuel, the velocity of the atomizing fluid at the point of intermixturewith fuel, and the exit velocity of fuel and atomizing fluid mixturefrom the nozzle. The last two of these factors are controlled by theproper proportioning of the size of the passages through the nozzle inrelation to the first two factors. In order to produce an axially shortflame, the exit velocity of atomizing fluid and fuel mixture must below, in the range of 325 to 400 feet per second. I have dis covered thatto produce such an exit velocity the velocity of the atomizing fluid'atthe point of intermixture with the liquid fuel should be between 650 and800 feet per second, the optimum being approximately 725 feet per secondand variations in velocity beyond this range resulting in inefficientburner operation or impin-gement of fuel on the surrounding surfaces.The atomizing fluid velocity at the point of intermixture with theliquid is controlled by proportioning the total cross-sectional area ofthe atomizing fluid jet passages in accordance with quantity ofatomizing fluid necessary at the rated capacity of the burner.

Optimum 'atomization of the liquid fuel 4is produced when the ratio byweight of atomizing fluid to fuel is 0.2 to 1.0 at maximum burnerrating, the minimum practical ratio being 0.18 to 1.0. A ratio above 0.2to 1.0 produces no undesirable results other than requiring increasedsize of atomizing fluid passages within the injector assembly butproduces no significant improvement in atomization of the fuel.

The ratio of the total cross-sectional area of atomizing fluid jetpassages at the point of interinixture with the liquid fuel to thenozzle exit orifice cross-sectional area. is preferably in the orde'r of1 to 2 produce optimum operating results.

As applied to the nozzle structure shown in Figures 8 to 12, thecross-sectional area of slots 134 at their juncture with passages 135 issuch that a velocity of atomizing fluid at that point is within therange of 650 to 800 feet per second, a velocity of 725 feet per secondat that point producing optimum results. The atomizing fluid supplypressure is maintained substantially constant throughout the operatingrange 'of the burner so that lthese velocities remain substantiallyconstant to maintain optimum -fuel atomization. The fuel supply rate isof course varied in accordance with the load upon the burner. The crosssectional area of the outlet orifice at edge 141 is approximately twice'the` aggregate cross-sectional area of the several slots 134 at theirpoints of juncture with passages 135, a range of from 1.65 to 1.0 to 2.3to l constituting the range of practical proportions. Such an outletorilice size produces the desired exit velocity range of from 325 to 400feet per second. The cross section area of the opening of cap 121 atedge 138 is preferably from 1.35 to 1.25 times the area of the orificedefined by edge 141 of body member 122.

In order to prevent coking of liquid fuel in the slots 134 and passages135 of the nozzle after burner operation is terminated, it is necessaryto prevent transmission of heat from the refractory lining 20 of thefurnace to the walls dening these fuel channels. In the past, effortshave been made to prevent this heat transmission by shielding the nozzlefrom the refractory lining and by retracting the nozzle from thefurnace. Neither of the solutions has proved to be completelysatisfactory. l have solved this problem by providing a nozzle of suchconstruction and formed of such suitable materials that heattransmission paths are formed by the nozzle assembly for rapidlyconducting heat from the nozzle to the air plenum walls for dissipationand that heat blocks are formed to prevent transmission of heat from theheat transmission channels to the walls within the nozzle which definethe fuel channels.

The heat transmitting paths are defined in the injector 96 of thepresent invention by body member 122, the end portion of which issubjected to the heat from the refractory furnace lining, and by conduit98 which are both formed of metals which transmit heat readily. Conduit9S is preferably formed of red brass or aluminum and body member 122 ispreferably formed of beryllium copper due to its high thermalconductivity, machineability and to the fact that it will retain sharpmachined edges over long periods of use. Core 120 and cap 121 are bothformed of a non-corrosive material having a low4 coeliicient thermalconductivity to inhibit transmission of heat from body member 122 to thesurfaces deiining the fuel channels. Stainless steel has been found tobe particularly suitable for this purpose. The engaged threaded portionsof conduit 98 and body member 122 are longer than required by thestructural strength requirements to provide a large area of contact forheat transfer` between the two members. The transfer of heat to conduit98 preheats the atomzing fluid during burner operation and results inmore eliicient overall operation.

As previously pointed out, certain diliiculties have also resulted inprior art devices from the slow leakage of oil from the end of the oilsupply tube into the atomizing fluid passages and out of the nozzle intothe furnace after termination of burner operation. In order to eliminatethis leakage, l have provided a fuel stop 150 in an enlarged end bore151 of the conduit 10i) which permits substantially free liow of fuelunder pressure but which prevents leakage of fuel from the conduit whenthe pressurized liquid fuel supply is cut-off. The fuel liow darn 150 isshown in perspective in Figure 14. Flow darn 150 consists of an uppersegmental disc 152 and a lower segmental disc 154 coaxially aligned andjoined by a small cylindrical portion 156. The stop 150 is mountedwithin the end of conduit 100 in such a position that the chordalsurfaces 158 and 169 are horizontal. segmental disc 152 abuts againstthe annular end wall 161 of bore 151 to maintain `proper axial alignmentbetween flow dam 150 and conduit ltlt) during assembly. The arcuatesurfaces of the segmental discs 152 and 154 are joined in sealedrelation to the linternal wall'of conduit 100 as by soldering to preventleakage of' oil and air between the conduit wall and the arcuatesurfaces.

During burner operation, the liquid fuel flows under surface 158,upwardly around the sides of the cylindrical portion 156 and oversurface 160 into end bore 124 of core 120. When the fuel supply iscut-olf, lower segmental disc 154 prevents leakage of the fuel from thebottom half of conduit and the upper segmental disc 152 preventsentrance of air, steam, or other liquid displacing material into the tophalf of conduit 100. Fuel flow over the surface is prevented because theatmospheric pressure of the air exerted upon the horizontal fuel surfacebetween discs 152 and 154 on each side of the cylindrical portion 156 issufficient to overcome the liuid pressure head produced by the portionof the fuel in lthe conduit 100 behind disc 152 but above the level ofchordal surface 160.

v As previously pointed out, the velocity values given for the gaseousfuel liow and primary and secondary air flow, with the exception of theair input velocity to the air plenum, are for maximum rated load of theburner.`

These velocities will be proportionately lower at lower loads but, dueto the improved nature of the combustion air and gaseous fuel flow guidestructure previously described, the same eicient air and fuel patternswill be maintained throughout the wide operating range of the burner.For example, the standard Power Boiler Output Test of the AmericanSociety of Mechanical Engineers has shown that the efliciency of thedisclosed burner increases from 83.5% at maximum load to 89% at onethirdof maximum load.

I have, therefore, disclosed a fuel burner adapted to burn either liquidor gaseous fuels individually or alternatively and which maintains ahigh level of combustiony eiliciency throughout its operating range.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. In a liquid fuel atomzing injector assembly, a conduit for supplyingliquid fuel; a surrounding conduit for atomzing fluid formed of metalhaving a high coeicient of thermal conductivity; a core member formed ofmetal having a low thermal conductivity coeliicient, provided withseparate liquid fuel and atomizingvliuid passages connected to saidconduit and having anend abutting the discharge end of said fuelconduit; a `cap member seated on the end of said core member and beingformed of metal having a low thermal conductivity coefficient; a bodymember formed of metal having a high thermal conductivity coefficientsurrounding said cap `and. core members, and secured to said atomzingfluid conduit to clamp said members in tight assembly against the endsof said conduits, said cap and body members having mating recessesformed in their adjacent surfaces defining `a mixing dome coaxial withsaid members, said body member having an orifice formed therethroughcoaxial with said dome, slots in the contacting surfaces of said cap andcore members providing atomzing fluid introduction passages into saiddome, and oil` introduction passages in said core intersecting saidintroduction passages intermediate their ends.

2. The combination as defined in claim 1 wherein said atomzing fluidconduit is formed of aluminum.

3. The combination as delined in claim 1 wherein said atomzing iiuidconduit is formed of red brass.

4. The combination as dened in claim 1 wherein said body member isformed of beryllium copper.

5. The combination as defined in claim 1 wherein said core and capmembers are formed of stainless steel.

6. The combination as defined in clairn 1 wherein said body member isformed of beryllium copper, said cap and core members are formed ofstainless steel, and said atomizing fluid conduit is formed of redbrass.

7. A fuel injector assembly for a liquid fuel burner comprising anatomizing fluid supply tube, an oil supply tube positionedconcentrically therein to define an oil passage through the latter andan annular air passage therebetween, an atomizing nozzle assemblymounted on said tube at one end containing passages for intermixing 'theoil and atomizing fluid vand discharging a spirally mist of intermixedatomizing fluid and oil particles for injection into a burner, flow dammeans in the end of said oil supply tube adjacent said nozzle forpreventing the entrance of gas into the upper portion thereof when theburner is inoperative, and means intermediate said first means and thedischarge end of said oil supply tube vfor preventing the leakage of oilfrom the lower portion of said tube when the burner is inoperative.

8. In a liquid burner, a fuel injector comprising a fuel atomizingnozzle, a fuel supply conduit and an atomizing fluid supply conduitconnected thereto at their discharge ends, and a fuel ilow darn fixedlymounted within the discharge end of said fuel supply conduit forpreventing leakage of fuel therefrom into said nozzle while the burneris inoperative, said dam comprising a plate member of substantial depthblocking the lower portion of the channel of said conduit.

9. In a liquid fuel burner, a fuel injector comprising a fuel atomizingnozzle, a fuel supply conduit and an atomizing fluid supply conduitconnected thereto at their discharge ends, and a fuel flow dam mountedwithin the discharge end of said fuel supply conduit for preventingleakage of fuel therefrom into said nozzle while the burner isinoperative, said fuel supply conduit being tubular in form andsupported in a horizontal position and said fuel flow dam comprising anupper and a lower segmental disk mounted concentrically and in axiallyspaced relation within the discharge end of said fuel supply conduit,the chordal surfaces of SaidV segmental disks being horizontal, theplane of the chordal surface of said upper disk being slightly below theplane of the chordal surface of the lower disk, and the arcuate surfacesof said disks being fixed in sealed relation to the internal wall ofsaid conduit.

-10. In a liquid fuel burner, a fuel injector comprising a fuelatomizing nozzle, a fuel supply conduit connected at its discharge endtosaid atomizing nozzle, and a fuel flow dam mounted in fixed relationwithin the discharge end of said fuel supply conduit for fpreventingleakage of fuel therefrom into said nozzle while the burner isinoperative, said dam comprising a plate member of substantial depthblocking the lower portion of the channel of said conduit.

11. In a liquid burner, a fuel injector comprising a fuel atomizingnozzle, a horizontally extending fuel supply conduit connected at itsdischarge end to said nozzle, flow dam means in the end of said fuelsupply conduit adjacent said nozzle for preventing the entrance of gasinto the upper portion thereof when the burner is inoperative, and flowdam means intermediate said first means and the discharge end of saidfuel supply conduit for preventing the leakage of fuel from the lowerportion of said Conduit when the burner is inoperative.

12. A liquid fuel injector comprising a fuel supply conduit, anatomizing fluid conduit, a fuel atomizer at the outlet of said conduitsembodying intersecting fuel and fluid passages to effect fuelatomi'zation, means for preventing leakage of fuel from said conduitinto said atomizer after termination of burner operation, a 4thermalshield enveloping s'aid atomizer passage intersection andcompri'singinner andA outer layers of relatively low and relatively highthermal "conductivity material respectively, and means thermallyisolated from said conduit for con- 12 ducting heat from said shieldouter layer and dissipating said heat in a'region remote from saidatomizer.

13. A fuel injector assembly for use in a fuel burner comprising a fuelatomizer formed of low thermal conductivity material and `formed withintersecting fuel and atomizing fluid channels to effect fuelatomization, a conduit for directing fuel to said atomizer fuel channel,a conduit for directing atomizing fluid to said atomizer atomizing fluidchannel, a shield of high thermal conductivity material enveloping saidatomizer, and means forming a high lthermal conductivity path extendingbetween said shield and a region of the burner remote and substantiallycooler than the region of said atomizer and a-dapted to transfer heatfrom said shield to said cooler burner region for dissipation.

14. In combination with a fuel burner structure, a liquid fuel injectorVcomprising a fuel supply conduit, means formed of low thermalconductivity material at the outlet end of said conduit for atomizingfuel discharged from said fuel conduit outlet end, and shield meansformed of material of higher thermal conductivity than the material ofsaid atomizing means enveloping said atomizing means, and a body ofmetal of relatively high thermal conductivity connected at one end tosaid shield means and extending therefrom to a region of said burnerstructure remote from said atomizer and substantially cooler than theregion of said atomizer and adapted to conduct heat from said shield tosaid burner structure region.

15. For use in a refractory lined furnace; a liquid fuel burnerincluding an atomizing fuel injector comprising a `fuel 'supply conduitand a fuel atomizer at 'the outlet yend of said conduit; and means forpreventing coking of fuel in said atomizer and conduit due to furnacerefractory lining heat after termination of burner operation comprisingmeans formed of material of relatively low thermal conductivity defininga first shield about the fuel passages in said atomizer; and meansformed of material of relatively high thermal conductivity defining asecond shield positioned about said first shield so as to be normallyinterposed between the refractory lining when in operative position, andsaid first shield, said atomizer and the outlet end of said conduit; andmeans, formed of material of relatively high thermal conductivityconnected `to said second shield and thermally isolated from saidconduit for forming, when in operative position, a heat transmissionpath between said second shield and a relatively large heat dissipatingbody portion of the burner located in the relatively cool zone remotefrom the refractory lining.

References Cited in the file of this patent UNITED STATES PATENTS448,460 Goujon Mar. 17, 1891 630,320 Billow Aug. 8, 1899 901,597 DohertyOct. 20, 1908 1,310,970 Stroud July 22, 1919 1,449,840 Reid Mar. 27,1923 1,665,786 Irish Apr. 10, 1928 1,770,232 Fegley July 8, 19301,789,977 Hopkins Jan. 27, 1931 1,841,698 Barber Jan. 19, 1932 1,972,537Rufe Sept. 4, 1934 2,098,487 Cooper Nov. 9, l1937 2,103,958 StillmanDec. 28, 1937 2,117,512 Scott May 17, 1938 2,124,443 Wotring July 19,1938 2,167,183 Naab et al July 25, 1939 2,206,070 Andler July 2, 19402,242,797 Lucke May 20, 1941 2,254,123 Soaper Aug. `26, 194,1 2,368,490Patterson Jan. 30, 1945 2,391,220 Beek Dec. 18, 1945 (Other referenceson following page) 13 UNITED STATES PATENTS Nagel Apr. 22, 1947 Lum Mar.2, 1948 Anderson Apr. 13, 1948 Williams Nov. 3o, 1948 5 Urquhart Jan.11, 1949 Raskin Oct. 25, 1949

